If there could be a unifying theme to 2014 in pop music -- and in a fractured pop culture world, there may no longer be "unifying themes" -- it might have been found in the run of fall hit singles like "Anaconda" by Nicki Minaj, "All About That Bass" by Meghan Trainor (whose album was released on Tuesday) and, going the direct route, "Booty" by Jennifer Lopez.

It's not that the butt was big that is newsworthy, but the response; for possibly the first time since Glenn Miller and His Orchestra's "It Must Be Jelly ('Cause Jam Don't Shake Like That)" in 1942, an upswing in backside-related pop hits was not accompanied by pearl-clutching and fainting spells.

How did we get from the big band era to "a-- so fat that you could see it from the front"? Let's look at the timeline:

Through the 1960s

B.B. (Before Butts)

This doesn't mean that the decades before the 1970s were completely glute-free ("Shake a Tail Feather," originally released in 1963, was not about dancing birds), but a culture scandalized by Elvis' hips wasn't quite ready for songs like Major Lazer's "Bubble Butt."

If a song was going to make it to the mostly-buttless mainstream, it was going to have to be both upbeat and more about dancing than about objectification. Even with that, it took a song as irresistibly catchy as KC and the Sunshine Band's "(Shake Shake Shake) Shake Your Booty" to cross over. Before the decade was out, Queen's ode to "Fat Bottomed Girls" had cracked the Billboard charts as well, and its more direct admiration would pave the way for songs to follow.

1980s

Rise of the Rump

Songs about the backside started to come into their own in the '80s, and they usually came from one of two perspectives. Either the track was in tribute to the tush, like LL Cool J's "Big Ole Butt," or involved a dance, like E.U.'s classic (and underrated wedding song -- no, really!) "Da Butt."

1990s

Music's Got Back

Starting from 1992's double shot of "Baby Got Back" by Sir Mix-a-Lot and "Rump Shaker" by Wreckx-n-Effect, the '90s were to booty-centric songs what the '50s were to the Yankees. R&B gave us "Thong Song" by Sisqo. Hip-hop gave us Mystikal's "Shake That A--" and Juvenile's "Back That A-- Up"; even "conscious" rappers got in the game, like Mos Def with "Ms. Fat Booty." Jennifer Lopez went from Fly Girl to movie star partially based on the Platonic ideal of a butt. The decade even gave us one of the most memorable tributes to the power of the derrière, in Bell Biv DeVoe's "Poison": "Never trust a big butt and a smile."

2000s

Butt Pride

"Bootylicious" was not the first instance of women, in this case Destiny's Child, bragging about the shape of their backsides. It was, however, a smash hit that set up a decade (and longer) of songs about positive body image. It also saw tributes to the gluteus transcend pop music, with Trace Adkins' "Honky Tonk Badonkadonk."